4.1 questions: subqueries which use dual

[<ric]

Mysql,
    Selecting from `dual` with a simple query works fine,

mysql> select 1 x from dual;
+---+
| x |
+---+
| 1 |
+---+

but within a derived table,

mysql> select * from (select 1 x from dual) s;
ERROR 1146: Table 'test.dual' doesn't exist

Is this an oversight or is it purposefully so?

Thank you,
    Richard.